Phosphites has been shown to be a new environmentally friendly chemical agent for crops, which could have increased their yield and resistance to disease. In this paper, the application and mechanism of phosphites as fungicides and functional fertilizers in agriculture are reviewed. The results show that phosphites have been widely used in plant diseases and pest control and plant nutrition in foreign countries. In China, its related research and application is lagging behind. Phosphoric acid as a bactericide in the inhibition of oomycetes such as Solanaceae, Brassica and other leafy vegetables has a good effect, while in the aspects of increasing the flowering, the yield, the fruit size and the soluble matter content of the strawberry, potato and other crops, it also has a good fertilizer effect. Mechanism studies have shown that phosphorous phosphates can be transported in the crop xylem and phloem of the two channels to speed up the absorption and utilization of nutrients;in disease resistance, the researchers generally believe that phosphite phosphate can induce crops to produce toxins and pathogenesis-related protein (PR protein), relying on salicylic acid (SA)to open the defense mechanism, so that crops can produce sustained immunity on the pathogen, but there is no clear conclusion until now. The results of this study could provide a reference for the promotion and application of phosphite in agriculture in China.